Force networks may underlie the constitutive relations among granular solids and granular flows and inter-state transitions.However, it is difficult to effectively describe the anisotropy of force networks.We propose a new pair correlation function g(r,θ) to describe the characteristic lengths and orientations of force chains that are composed of particles with contact forces greater than the threshold values.A formulation g(r,θ)≈a(r) + b( r ) cos 2(θ-π/2) is used to fit the g(r,θ) data.The characteristic lengths and orientations of force networks are then elucidated.